The present invention relates to a recording apparatus for forming an image in the form of letters, graphic figures or the like on a photosensitive recording medium with using a mask member formed of a light transmissive member on which a light shielding mask image is carried.
Generally known recording apparatus for use as color copying machines may be classified into silver-salt photographic recording apparatus, thermal transfer recording apparatus and electrophotographic recording apparatus. The silver-salt photographic recording apparatus can produce images of good quality but requires a long period of time for forming an image and are expensive to manufacture. The thermal transfer recording apparatus produces images of poor color reproducibility, since they are formed by overlapping three colors. The electrophotographic recording apparatus can copy an image at highest speed with high resolution, but are expensive and requires high running cost due to maintenance.
To overcome the aforesaid drawbacks of the conventional image recording apparatus, there has been proposed a recording apparatus of another type which can produce images of good color reproducibility and which is inexpensive and facilitates maintenance. In this recording apparatus, mask members based on image data in red, green, and blue are printed on a thermosensitive recording sheet by a thermal head, and a photosensitive pressure sensitive recording medium or sheet coated with coloring materials is exposed to light successively through the mask members to form a latent image on the photosensitive pressure sensitive sheet. Thereafter, the latent image is developed into a visible color image under pressure. Such image recording apparatus using the light shieldable mask member is also disclosed in commonly assigned copending U.S. patent application Ser. Nos. 50,313, now U.S. Pat. No. 4,810,614, filed on May 14, 1987 and 157,740, now U.S. Pat. No. 4,785,316, filed on Feb. 18, 1988.
In the image recording apparatus of the another type, it is of vital importance to position the three different mask members exactly with respect to the identical portion of the photosensitive pressure sensitive sheet. This positioning process is technically highly difficult to achieve, since the accuracy level has to be quite high such as within an error of 20 .mu.m or less. Unless the mask members are positioned highly accurately with respect to the photosensitive pressure sensitive sheet, no sharp and detailed color image will be formed on the sensitive sheet.